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Subject: Re: [PATCH net-next 0/8] Improve GbEth performance on Renesas RZ/G2L
 and related SoCs
To: Paul Barker <paul.barker.ct@bp.renesas.com>, "David S. Miller"
	<davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Jakub Kicinski
	<kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
CC: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>, Wolfram Sang
	<wsa+renesas@sang-engineering.com>, <netdev@vger.kernel.org>,
	<linux-renesas-soc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20240131170523.30048-1-paul.barker.ct@bp.renesas.com>
From: Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <a428e75e-32b7-e94e-24c3-f87097951470@omp.ru>
Date: Thu, 1 Feb 2024 22:22:39 +0300
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On 1/31/24 8:05 PM, Paul Barker wrote:

> This series aims to improve peformance of the GbEth IP in the Renesas

   Performance.

> RZ/G2L SoC family and the RZ/G3S SoC, which use the ravb driver. Along
> the way, we do some refactoring and ensure that napi_complete_done() is
> used in accordance with the NAPI documentation.
> 
> Performance improvment mainly comes from enabling SW IRQ Coalescing for

   Improvement.

> all SoCs using the GbEth IP, and NAPI Threaded mode for single core SoCs
> using the GbEth IP. These can be enabled/disabled at runtime via sysfs,
> but our goal is to set sensible defaults which get good performance on
> the affected SoCs.
> 
> Changes are made specific to the GbEth IP, avoiding potential impact on
> the other Renesas R-Car based SoCs which also use the ravb driver. This
> follows the principle of only submitting patches that we can fully test.
> 
> The performance impact of this series on iperf3 testing is as follows:
>   * RZ/G2L Ethernet throughput is unchanged, but CPU usage drops:
>       * Bidirectional and TCP RX: 6.5% less CPU usage
>       * UDP RX: 10% less CPU usage
> 
>   * RZ/G2UL and RZ/G3S Ethernet throughput is increased for all test
>     cases except UDP TX, which suffers a slight loss:
>       * TCP TX: 32% more throughput
>       * TCP RX: 11% more throughput
>       * UDP TX: 10% less throughput
>       * UDP RX: 10183% more throughput - the previous throughput of

   10183%, really? 8-)

>         1.06Mbps is what prompted this work.
> 
>   * RZ/G2N CPU usage and Ethernet throughput is unchanged (tested as a
>     representative of the SoCs which use the R-Car based RAVB IP).
> 
> This series depends on:
>   * "net: ravb: Let IP-specific receive function to interrogate descriptors" v5
>     https://lore.kernel.org/all/20240131084133.1671440-2-claudiu.beznea.uj@bp.renesas.com/

   So this is based on yet unmerged patch?
   Dave, Jakub, et al., the series should be considered RFC then.

> To get the results shown above, you'll also need:
>   * "topology: Set capacity_freq_ref in all cases"
>     https://lore.kernel.org/all/20240117190545.596057-1-vincent.guittot@linaro.org/
> 
>   * "ravb: Add Rx checksum offload support" v2
>     https://lore.kernel.org/all/20240124102115.132154-2-biju.das.jz@bp.renesas.com/
> 
>   * "ravb: Add Tx checksum offload support" v2
>     https://lore.kernel.org/all/20240124102115.132154-3-biju.das.jz@bp.renesas.com/

   Those 2 are not finalized yet...

> Work in this area will continue, in particular we expect to improve
> TCP/UDP RX performance further with future changes to RX buffer
> handling.
> 
> Paul Barker (8):
>   net: ravb: Split R-Car & GbEth poll functions
>   net: ravb: Simplify GbEth poll & receive functions
>   net: ravb: Count packets in GbEth RX (not descriptors)
>   net: ravb: Always process TX descriptor ring in GbEth poll
>   net: ravb: Always update error counters
>   net: ravb: Align GbEth poll function with NAPI docs
>   net: ravb: Enable SW IRQ Coalescing for GbEth
>   net: ravb: Use NAPI threaded mode on 1-core CPUs with GbEth IP
> 
>  drivers/net/ethernet/renesas/ravb.h      |   3 +-
>  drivers/net/ethernet/renesas/ravb_main.c | 103 ++++++++++++++++-------
>  2 files changed, 74 insertions(+), 32 deletions(-)

MBR, Sergey